A highly sensitive manual outlining detainee interrogation methods the FBI fought to keep secret for years was hiding in plain sight at the Library of Congress - open to the public, but unnoticed until now. CNN's Joe Johns reports.

It's one week after Aaron Alexis opened fire at the Navy Yard in Washington, DC, and we are finally getting some answers to the question, "Why?" At a press conference today, the FBI released chilling new video of Alexis and discussed what may have led to his attack– the voices he heard, the markings on his weapons, and the electromagnetic waves that he claims were controlling him.

CNN's Joe Johns reports on the "delusional" man and tries to piece together a motive.